Agglomerated product with paper fibers

ABSTRACT

A conglomerated material based on metallurgical by-products and characterized in that it contains 2-10% of fibers, 9-25% wt of an alkaline earth metal hydroxide, and % wt of water.

The present invention relates to an agglomerated product containing,among others, fibers and a calcium derivative.

Document EP-A-0,272,242 describes an agglomerated product containing CaOand from 0.5 to 10% by weight of cellulose fibers as binder. Accordingto this document the use of fibers makes it possible to increase, on theone hand, the resilience of the agglomerated product and, on the otherhand, the reactivity of the agglomerated product.

Tests carried out by the Applicant have shown that an agglomeratedproduct containing metallurgical dust and fibers exhibited a betterresilience than an agglomerated product containing only metallurgicaldust.

Metallurgical dust is intended to mean dust originating from industriesor techniques which ensure the manufacture or the use of metals, itbeing possible for this dust to be metallic or otherwise, originatingfrom ferrous or nonferrous metals.

Unexpectedly, the Applicant has noticed that it is possible to increasefurther the resilience of an agglomerated product containingmetallurgical dust and fibers by adding an alkaline-earth metalhydroxide, in particular calcium hydroxide, to the said agglomeratedproduct.

The agglomerated product according to the invention is an agglomeratedproduct based on metallurgical dust additionally containing fibers andat least one hydroxide of an alkaline-earth metal.

In one embodiment the agglomerated product in accordance with theinvention contains less than 75% by weight, advantageously from 0.5 to20% by weight, preferably approximately 10% by weight of alkaline-earthmetal hydroxide.

The weight content of fibers in the agglomerated product isadvantageously lower than 20%, preferably between 0.5 and 10%.

In an advantageous embodiment the agglomerated product contains water,the moisture content of the product in accordance with the inventionbeing advantageously lower than 20% by weight, preferably lower than 10%by weight, in particular between 5 and 10% by weight.

The alkaline-earth metal hydroxide is preferably calcium hydroxide suchas a calcium hydroxide obtained by slaking of 1 part by weight of CaO orof CaO.MgO with approximately 0.7-0.8 part by weight of water,optionally in the presence of additives such as an amine or anaminoalcohol. The calcium hydroxide may therefore be in the formCa(OH)₂.MgO or Ca(OH)₂.Mg(OH)₂.

Another subject of the present invention is a process for thepreparation of an agglomerated product in accordance with the invention,in which a mixture of metallurgical dust, of fibers and of analkaline-earth metal hydroxide is prepared and in which the said mixtureis subjected to a compression.

Examples of fibers which can be employed in the product in accordancewith the invention are: synthetic fibers such as glass fibers, carbonfiber, boron fibers, silicon carbide fibers, aramid, polyamide andphenolic fibers, polyalkyl (for example polyethylene, polypropylene)fibers, polyester fibers, acrylic, cellulosic, acetate, rayon andviscous fibers, fibers of vegetable origin such as sisal, jute, flax,cotton, wood, paper produced from wood, fibers of mineral origin such asasbestos, and metal fibers.

The fibers employed are preferably cellulosic fibers such as wood orpaper fibers.

Metallurgical derivatives denote, among others, dry dust or dust of lowmoisture content (for example less than 10%) from the metallurgicalindustry, in particular from the iron and steel industry, such as slag,blast furnace dust, sludge obtained during the removal of dust from thefumes leaving converters (dust removal by a dry or wet route), andpulverulent or nonpulverulent products originating from catalystscontaining metals employed in the chemical, in particular petrochemical,industry (cracking catalysts and the like).

As is known, the metallurgical derivative may be at the same time in theform of a dry (preferably pulverulent) powder and in the form of asludge.

In the case of a powder, the mixture in the process according to theinvention can be prepared merely by mixing or blending, for example, 10parts by weight of metallurgical duet, less than 3 parts by weight ofalkaline-earth metal hydroxide and at least one part by weight offibers.

In the case of a sludge said mixture is advantageously prepared bymixing said sludge containing metallurgical dust with fibers and analkaline-earth metal oxide (in particular CaO and CaO.MgO). In contactwith water, the oxide is converted into hydroxide with drying of thesludge due, on the one hand, to the absorption of water and, on theother hand, to the evaporation of water, the latter being due to theheat released by the exothermic reaction.

The moisture content of the mixture is preferably adjusted to a valuelower than 20%, preferably 10%.

This adjustment can be carried out by drying the metallurgical dust, butis preferably carried out by adding an appropriate quantity of analkaline-earth metal oxide (for example CaO and/or CaO.MgO) so as toavoid the high costs inherent in a drying stage.

In the case of said sludge, in an embodiment of the process inaccordance with the invention said mixture is prepared by means of CaOand/or MgO and fibers, in particular of CaO and/or MgO containing from0.5 to 10% by weight of cellulose fibers.

Other special features and details of the invention will emerge from thedetailed description of the following examples of preparation:

EXAMPLE 1

A powder originating from a byproduct of the treatment of catalystscontaining, among others, molybdenum, nickel, vanadium and aluminum wasdried until the moisture content of the powder was lowered to a value ofthe order of 5%.

This powder was next mixed with calcium hydroxide in the form of(Ca(OH)₂.MgO) and paper fibers so as to obtain a mixture whosecomposition was as follows:

    ______________________________________                                        powder (in dry form) 78% by weight                                            moisture             5% by weight                                             Ca(OH).sub.2.MgO     15% by weight                                            paper fibers         2% by weight                                             ______________________________________                                    

This mixture was next converted into a briquette or agglomerated productwith the aid of a roller press, the pressure exerted on the mixturebetween the rollers being approximately 10 tons per linear centimeter ofthe rollers.

The agglomerated product had a relative density of 1.95 and acompressive strength of 2068N (crushing strength of the ovoid briquettebetween the platens of a press).

By way of comparison, agglomerated products containing no fibers and/orno Ca(OH)₂ MgO were prepared as described above,

Table 1, which follows, gives the resilience and the relative density ofvarious agglomerated products.

                                      TABLE 1                                     __________________________________________________________________________    Composition of the agglomerated product                                                                       Compressive                                   in % by weight            Relative                                                                            strength                                      Dust     Ca(OH).sub.2                                                                       H.sub.2 O moisture                                                                    Fibers                                                                            density                                                                             N                                             __________________________________________________________________________    1    100 0    0       0   1.79  568                                           2    98  0    0       2   1.79  1078                                          3    93  0    5       2   1.95  1470                                          4    80  15   5       0   1.95  1078                                          The  78  15   5       2   1.95  2068                                          invention                                                                     __________________________________________________________________________

From this table it follows that the combined use of Ca(OH)₂.MgO and offibers makes it possible to obtain an agglomerated product exhibiting avery high crushing strength when compared with that of an agglomeratedproduct containing either Ca(OH)₂.MgO or fibers or containing neither. Aperson skilled in the art could not expect to obtain an agglomeratedproduct exhibiting a compressive strength higher than 2000N, whereas theuse of fibers or of Ca(OH)₂ alone made it possible to obtain only anagglomerated product whose compressive strength is lower than 1500N.

EXAMPLE 2

The operation was carried out as described in Example 1, except that theCa(OH)₂.MgO content was 24% instead of 15%,

The agglomerated product, whose composition was as follows: 69%metallurgical dust, 24% Ca(OH)₂.MgO, 2% of fibers and 5% of moisture,had the following properties:

relative density: 1.95

compressive strength: 2009N

These values are comparable with those obtained for the agglomeratedproduct in accordance with the invention of Example 1.

EXAMPLE 3

A byproduct of treatment of catalysts containing molybdenum, nickel,vanadium and aluminum was dried by an instantaneous drying process. Thisbyproduct was mixed in a plow head mixer of 80 liter capacity withfibers and an alkaline-earth metal hydroxide. A mixture exhibiting agood fiber distribution was obtained after 5 minutes.

The mixture thus prepared was next converted into cushion-shapedbriquettes (45×40×25 mm) by means of a roller press with 3 cavities, thepressure exerted between the rollers being 12 tons per linear cm.

Agglomerated products of different composition were thus prepared. Table3, which follows, gives the composition of said agglomerated productstogether with their relative density, their compressive strength and thefraction F in % of the products which have a particle size greater than10 mm after 4 drops from a height of 2 m.

                                      TABLE 2                                     __________________________________________________________________________    Composition (%)      Paper                                                                             Relative                                                                            Strength                                                                           F                                         Dust                                                                             H.sub.2 O                                                                         Ca(OH).sub.2                                                                       Ca(OH).sub.2.MgO                                                                       fiber                                                                             density                                                                             newton                                                                             %                                         __________________________________________________________________________    77 6        15       2   2.18  2482 95.6                                      75.7                                                                             7.3      15       2   2.18  2482 95.6                                      75.2                                                                             7.8      15       2   2.22  3280 95.5                                      76.2                                                                             7.3      15       1.5 2.16  2697 92.2                                      74.5                                                                             8        15       2.5 2.18  3060 98                                        80.7                                                                             7.3      10       2   2.19  2710 94                                        78.2                                                                             7.3      12.5     2   2.21  2666 95                                        79.4                                                                             8.1 10            2.5 2.21  3280 98                                        81.4                                                                             8.6 7.5           2.5 2.17  3046 96.5                                      81.9                                                                             5.6 10            2.5 2.16  3462 98                                        __________________________________________________________________________

These tests show that the combined use of 15% Ca(OH)₂.MgO and of 2.5% offibers (that is to say an agglomerated product containing approximately10% of Ca(OH)₂.MgO calculated in the form of Ca(OH)₂ and 2.5% of fibers)or of 10% of Ca(OH)₂ and of 2.5% of fibers makes it possible to obtainoptimum values of strength and for the factor F, and that a moisturecontent of approximately 7% for Ca(OH)₂.MgO and of approximately 6% forCa(OH)₂ appear to be the optimum values for obtaining the best resultfor the strength and the factor F.

EXAMPLE 4

An agglomerated product was prepared as described in Example 1, exceptthat the dust employed was a hematite dust which had a moisture contentlower than 0.15% and that the compacting of 30 g of material in the formof a cylindrical prism of 3 cm diameter was performed under a pressureof 20 tons.

Agglomerated products containing various additives were thus prepared.Table 4, which follows, gives the composition of said agglomeratedproducts, as well as their strength. The latter was measured by pressinga rod in the center of the cylindrical prism (breakage test).

                  TABLE 3                                                         ______________________________________                                        Composition (by weight)                                                              Mois-   Paper             Relative                                                                             Strength                              Hematite                                                                             ture    fibers  Ca(OH).sub.2.MgO                                                                        density                                                                              N                                     ______________________________________                                        99.85  0.15                      3.26   29                                    97.85  0.15    2                 2.97   304                                   66.85  0.15            33        2.67   274                                   64.85  0.15    2       33        2.55   1205                                  63     2       2       33        2.36   1735                                  ______________________________________                                    

This table clearly shows that the combined use of a hydroxide of analkaline-earth metal and of fibers, in particular in the presence ofmoisture, makes it possible to obtain agglomerated products exhibiting acompressive strength which is higher than that of an agglomeratedproduct containing, as binder, either fibers or Ca(OH)₂.MgO.

We claim:
 1. An agglomerated product based on metallurgical by-productsconsisting of:2.5 to 3 % by weight, based on the total weight ofproduct, of paper fibers; 5 to 10 % by weight, based on the total weightof product, of water; Ca(OH)₂, the weight content being comprisedbetween 9 and 25 % by weight, based on the total weight of product, andthe remaining part consisting of metallurgical by-products.
 2. Theagglomerated product of claim 1 wherein Ca(OH)₂ is present in a rangebetween 10 and 20 % by weight, based upon the total weight of product.3. An agglomerated product based on metallurgical by-products consistingof:about 2.5% by weight, based on the total weight of product, of paperfibers; 5 to 10 % by weight, based on the total weight of product, ofwater; Ca(OH)₂, the weight content being about 10% by weight, based onthe total weight of product, and the remaining part consisting ofmetallurgical by-products.
 4. An agglomerated product based onmetallurgical by-products consisting of:2.5 to 3 % by weight, based onthe total weight of product, of paper fibers; about 10% by weight, basedon the total weight of product of Ca(OH)₂ ; from 5 to 8% by weight,based on the total weight of product, of water, and the remaining partconsisting of metallurgical dust.